The Composite Laminated Plate Layer Stress Analysis And Fatigue Life Estimates

There are various kinds of fatigue damages in the composite laminate structures, both in-plane and interlaminar. Their interaction and influence on fatigue life are very complicated issues. This paper first describes a fatigue life prediction method including only in-plane damages, This method was modified in this paper by the introduction of interlaminar stresses and the corresponding damage models.Two finite element modeling techniques have been evaluated for the interlaminar stress analysis of multidirectional composite laminates. In one of the techniques, each ply of a laminate is orthotropic in property and modeled by the 3D solid elements, with one element across its thickness. Another technique suggests that the laminate be modeled by a combination of 2D plate elements, MPC (rigid) elements and 1D spring elements, named mixed 1D/2D/MPC model. Both modeling techniques are effective and the mixed model is more suitable for the simulation of interlaminar damages.A simplified procedure to evaluate fatigue life of multidirectional laminate is suggested. The predicted fatigue life correlates well with the experimental results, much better than the former method ignoring interlaminar stresses and damages.